1. Field of the Invention
The present invention relates to a memory and an operating method thereof, and more particularly, to a non-volatile memory and a method for operating the same.
2. Description of the Related Art
The non-volatile memory, with such advantage as multiple data reading, writing, and erasing operations, and the data storage protection even when power is off, has become a widely used memory component in the personal computer and the electronic device.
Referring to FIG. 1, a schematic diagram of a non-volatile memory disclosed in U.S. Pat. No. 6,833,528 by Toshiyuki et al is shown. The non-volatile memory comprises two metal-oxide semiconductor (MOS) transistors, and each transistor comprises a p-well 101, an n-doped region (drain) 107A, and an n-doped region (source) 107B that are all formed on a silicon substrate. Wherein, one transistor is a select transistor composed of a gate insulating layer 102 and a select gate 103. The other transistor is a memory transistor composed of a bottom oxide layer 104a, a charge trapping layer 104b, a top oxide layer 104c (i.e. oxide-nitride-oxide, ONO), and a memory gate 105. The gates 103 and 105 are insulated by an insulating layer 106. In addition, a part of the select transistor is extended onto the memory transistor.
The non-volatile memory mentioned above has several problems. For example, when the hydrofluoric acid is used as an etching agent when fabricating the non-volatile memory mentioned above, the thickness of the top oxide layer 104c is hard to control. In addition, since the non-volatile memory has a two-layer gate, it is very hard to integrate the non-volatile memory into the general CMOS logic process. Moreover, since its gate has two layers, the manufacturing cost of the entire non-volatile memory is inevitably increased. Furthermore, since a part of the select transistor is extended onto the memory transistor, the alignment between the first gate and the second gate becomes a key success factor. If the alignment error increases, the channel length would further depart from the origin design, and the manufacturing process is more complicated.